The present invention relates to civil engineering and, more particularly, to methods and equipment for making filling piles. The invention is useful in laying foundations of concrete and reinforced concrete piles for apartment and industrial buildings, hydraulic structures and other facilities. 2. Description of the Prior Art
There is known a method for producing filling piles, wherein a hole is drilled in the ground to extend outside the drilled rock. A casing pipe, which serves to prevent crumbling of the hole walls, is placed in the hole and filled with a concrete mix. The concrete mix is compacted, and the casing pipe is pulled out (cf. accepted Federal Republic of Germany Application No 2,217,485, Cl. 84c, 5/38). The installation for effecting this method (ibid.) comprises a drilling machine, a concrete mix feeder, and a casing pipe provided with a ring means for compressing the concrete mix.
An important limitation of the above method is the necessity of drilling a hole. Another disadvantage of this method resides in the impossibility of making reinforced concrete piles. The installation for carrying out this method is too big and complicated.
There is known a more productive method of making filling piles, wherein a casing pipe is set on the ground and driven to a prescribed depth. Concrete mix is then fed into the casing pipe, and at the same time the latter is gradually pulled out and the mix is compacted (cf. USSR Inventor's Certificate No. 253,666, IPC E 02 d 5/40).
The installation for effecting the latter method (ibid) comprises a casing pipe coupled to a pile puller intended to set the pipe on the ground, support it and pull it from the ground, a pile driver intended to drive the casing pipe into the ground, and a concrete mix feeder intended to feed the concrete mix into the casing pipe as the latter is being pulled from the ground.
The pile driver comprises a vibrator mounted on the casing pipe and coupled to the pile puller. The vibrator makes the casing pipe vibrate along its axis, thereby driving the casing pipe down to a prescribed depth.
Fitted over the lower end of the casing pipe is a detachable tubular cap. Inside the cap there are radially extending ribs and a ring diaphragm.
As the casing pipe is pulled out, the radial ribs act on the concrete mix and compact it. The extraction of the casing pipe is periodically discontinued, and the pipe is dropped so that the ring diaphragm strikes the concrete mix and compacts it to a desired density.
In some cases the impact of the ring diaphragm drives the mix out of the hole, whereby the pile is made thicker and its carrying capacity is improved.
However, the foregoing method and equipment cannot ensure a high production rate, because the process of driving the casing pipe into the ground is relatively slow, and because the whole operation is further slowed down by the necessity to discontinue the extraction of the pile in order to compact the concrete mix.
Another disadvantage is that the ring diaphragm cannot compact the mix to a required degree, which accounts for a limited carrying capacity of the piles.
Though the method under review makes it possible to make piles with some portions thicker than the rest of the pile, it can be applied to soft soils only, because the impact capacity of the ring diaphragm is insufficient to overcome the resistance of hard ground. In addition, it is impossible to predict the size and shape of a broader portion of a pile to any reasonable degree of certainty.
Furthermore, the process under review is inapplicable to making piles of reinforced concrete, because the ribs and ring diaphragm considerably reduce the section of the internal channel of the casing pipe, which renders it difficult to squeeze a reinforcing cage through this channel into the hole.
Of course, a reinforcing cage could be fitted over the casing pipe, but the mechanical action by the vibrator transmitted to the ground through the casing pipe is insufficient to make a cavity around the casing pipe wide enough to accommodate the reinforcing cage.